In order to guarantee a certain amount of reliability for the connections made and avoid any disconnection, such connectors are fitted with a locking sleeve that is designed to co-operate with locking means provided by the complementary connector. Thus, the locking sleeve can make use of a bayonet locking system or may indeed include a thread for co-operating with a complementary thread of the complementary connector. Such a locking sleeve is thus movable in rotation between an unlocking position in which the connectors can be assembled or separated, and a locking position in which, once the connectors have been plugged together, it is no longer possible to separate them.
Such a locking sleeve gives full satisfaction in terms of its function of providing an obstacle to unwanted separated of connectors that are connected together. Nevertheless, under certain conditions of use, and in particular when the connectors that are connected together are subjected to various stresses in traction or in rotation, or indeed are subjected to vibration, it is found that the locking sleeve can itself go in unwanted manner from its locking position to its unlocking position where it is no longer capable of performing its function of making the connection secure.